Car manufacturers are racing not only the power of their engines, the number of pieces of equipment and design, but also the size of the wheels. Ferrari F40 once had a 15-inch rims, and until recently, 18-inch were reserved only for really fast cars. Today these rims you have a compact available, and less than 16 inches hardly anyone goes down. 14 inches it's actually an absolute minimum even in the segment A. It's only about an inch less than the standard wheels in the legendary Lamborghini Countach!
Why do big rims?
The diameter of the rim strongly affects the appearance of the car, and it has long been known that we buy by eyes. Thick tires are already out of fashion, they look unsightly, cars mudgargs are getting bigger and you need to fill them something nice, not black rubber. Another issue is the design requirements. Cars are getting bigger brakes, and they cease to be within the rims with a diameter of 15 inches. Still, very often it dominates excess of from over substance. Have a look at the wheels tested recently in the websites of Autokult.pl Audi S1 or S3. Cars equipped with 18- and 19-inch wheels. They are a bit too big in relation to the brake system that does not look attractive to the end and if someone is a purist, you should still order a bigger brakes. A cheaper and wiser is to go down to the size of about an inch below the rim and everything will be OK. But there are other, more rational reasons for using such large rims.
Besides the attractive design and the ability of containing large brakes, tires are also imporant. This low profile well suited to turning becasue the high rigidity of the side walls. And it is not about the material itself. Simply low wall in heavily inflated tire is not as flexible as high. Thanks to this in the turning the tire is not subjected to so-called lining effect. The result, at least in theory is better steering precision, better feel and greater sense of the car. However, it does not always work. Low profile, combined with large diameter rims makes that a car might have a problem with damping rough roads. This in turn hasn't a positive effect on the traction and so at the same corner but uneven road tire with a higher profile, not only can provide greater adhesiveness, but also a better feeling of the steering wheel. The car will be driving smoothly and not jumping up and down and battered putting it simply.
Tires with too low a profile may also negative affect the sense of the breaking adhesiveness in the unsport car. Hard / low tire can break adhesiveness more violently and without warning. Higher / soft tire more easily feel at the limit of adhesiveness, usually slide earlier, but it let you know.
And what about the off-road cars ?
Again the reasons for using large-diameter wheels and low-profile tires are similar. First visual effect. It is known that more and more rare roadster (about SUVs not to mention) leave the paved roads, and their main job is to look good. Equipped with a large mudgards arches for many people present themselves better if those wheel arches are well filled. The second issue is the brakes. These too are more and more effective, and thus, higher. And as once standard in SUVs were the wheels 15- or 16-inch, so today as the minimum deemed to 17-inch.
In the beginning was the problem, because the manufacturers off-road tires have not yet had products about a diameter of 17-inches, when they appeared, were expensive, and car users could not use smaller rims because of the brakes. The market has grown rapidly and today there are no problems with the purchase of mud rubber 18 inches in diameter. The problem arises when you need to drive with this tire in the terrain. It works not sideways, and it's a big disadvantages in the mud or in the sand.
The last thing is driving that in view of the increasing power of such vehicles and safety requirements had to be improved. And similar to a car tire with a lower profile, at least in theory, should provide better driving. Similarly, a low tire drives better on unevens than high. An interesting could be a really big off-road tires on rims recently tested by me the Toyota Hilux Arctic Truck. Size 315/70 R 17 may suggest that it is soft and does not allow for a fast ride on the corners. It turned out that the only problem was adhesiveness of the off-road tread. There was any trouble of sense with the car, precision steering and high-speed maneuvers at higher speed. The key was large track of wheels, width heavily inflated tires and a rigid suspension.
It is worth to remember that if the crossover has to ride in the wilderness, even small, it's always good to have a smaller diameter wheels and tires with a higher profile and a smaller width. These types of tires work better in every type of terrain, perhaps except very miry, dry sand. You can also purchase model tires of at least some off-road tread, as opposed to a 18- or 19-inch tires with low profile. The large rims also much easier to damage not only in the city on the curbs, but also in the terrain.
Disadvantages of the large-diameter wheels
Practice shows that the exaggeration in the size of the wheels does not always is all to the good. Often, large diameter wheels also entails a greater width of the tire. This in turn is reflected in the quality of driving. Increased width works in motorsport, but in everyday use not always. Independent results of various tests confirm that the largest size of the wheels does not always, or even rarely gives better performance than this indirect. This means that given a choice wheels 16-, 17- and 18-inch, we can not be absolutely certain that the 18-inch wheel will give the best adhesiveness, and the best may be 17-inch rim and tire of a similar size to a standard. And this applies not only wet but also dry conditions. Not always feels are the best at big wheels. An example would be small and extremely good at running the MINI Cooper S, which equipped a factory wheels with a diameter of 16 inches and tires with a width of 195 gives not only a wonderful of adhesiveness, but also a wonderful sense of the car in turnings and during sudden route changes.
Large diameter wheels are not completely working very well or in combination with low-profile tire in winter conditions. The old rule says that at the snow tires are better with smaller width, but it is a thing of the past. Manufacturers already make winter tires with a huge diameter and width. However, in extremely difficult conditions and so narrower, and also higher tire works better. High impact on the quality of driving has here its larger profile, consequently in higher flexibility of the tire, and thus also adhesiveness, for example, on uneven surfaces covered with compacted
snow. If the wheel has a smaller diameter, it also has a tendency to more accurately select the unevens (falls into a hole, which does not fall in a large circle), which also translates into a higher adhesiveness.
One of the major disadvantages of large-diameter rims is a drop in the level of comfort. I am talking not only about the too large size. One example may be mentioned MINI, which already on 17-inch rims with so much hardness of the suspension gets a bit annoying. Even worse memories of the BMW Active Tourer 218d M suspension and 18-inch wheels. Both elements clearly positive impact on the during of this minivan, but the springing was not pleasant. The family car with low springing comfort? No sense.
Large wheels make the suspension gets whacked. The tire also is an element of shock absorbing, one of the most important and the first, which receives impact from the road surface. If you lose this property as a result of reduction in profile, her role take over the rubber suspension elements. Unfortunately, this translates into faster wearing. Larger wheels put on the car with slight mileage can cause vibration, because clearances or beating, could not be sensed on a thick tire mounted on 15-inch rims may become clearly noticeable when you change the rims at 17- or 18-inch.